
document.onkeydown = function getKeyCode(event) {
    event = event || window.event;
    switch (event.keyCode) {
        case 8:
            event.preventDefault();
            fun_back();
            break;
        case 640:
            event.preventDefault();
            fun_back();
            break;
        case 13: //确定
            fun_enter();
            break;
        case 37: //左
            fun_left();
            break;
        case 38: // 上
            fun_up();
            break;
        case 39: // 右
            fun_right();
            break;
        case 40: // 下
            fun_down();
            break;
    }
};